Semiconductor chip with backside conductor structure

ABSTRACT

Various semiconductor devices and methods of testing such devices are disclosed. In one aspect, a method of manufacturing is provided that includes forming a bore from a backside of a semiconductor chip through a buried insulating layer and to a semiconductor device layer of the semiconductor chip. A conductor structure is formed in the bore to establish an electrically conductive pathway between the semiconductor device layer and the conductor structure. The conductor structure may provide a diagnostic pathway.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is divisional application of U.S. applicationSer. No. 12/237,568, filed on Sep. 25, 2008, the entire contents ofwhich are herein incorporated by reference.

1. FIELD OF THE INVENTION

This invention relates generally to semiconductor processing, and moreparticularly to structures and methods for testing areas of asemiconductor chip.

2. DESCRIPTION OF THE RELATED ART

Scanning probe microscopy is an umbrella term that covers severalscanning techniques used to diagnose semiconductor chips, such as,conducting atomic force microscopy, scanning spreading resistancemicroscopy, scanning capacitance microscopy and scanning tunnelingmicroscopy. These techniques are frequently used to perform diagnostictests on semiconductor chips, particularly, though not exclusively,after a semiconductor chip has been fabricated and subsequentlydeprocessed in order to expose circuit structures or other areas ofinterest that are slated for diagnostic examination. One requirementshared by most scanning probe microscopy techniques is a conductingpathway between a probe tip and a source of bias or voltage through thechip. In bulk semiconductor devices, the establishment of the requisiteconducting pathway is a relatively straight forward matter of attachinga conductor to the bulk semiconductor side of the chip and touching orbringing the probe tip in close proximity to an area of interest of theopposite side of the chip. However, the situation is more complex insemiconductor-on-insulator dice, particularly for certain types ofp-channel devices thereof. The difficulty stems from the fact that inmany conventional semiconductor-on-insulator designs with p-channeldevices, isolation structures are used to isolate one or perhaps a fewp-channel devices from adjacent devices. These isolation structures thenform laterally impenetrable barriers to conductive pathways that wouldordinarily be used for SPM analysis.

One conventional technique for performing SPM analysis on asemiconductor-on-insulator chip involves the formation of a via throughthe front side of the semiconductor chip. In this regard, thesemiconductor chip is deprocessed down to the active device layer and adeep trench is formed through the active device layer and penetratingthe buried insulating layer and

in a certain distance into the base semiconductor layer. Thisconventional technique provides a somewhat manageable system forperforming SPM analysis in a n-channel area that is not radicallysegregated by isolation structures. However, even in such relativelyopen n-channel areas, this conventional technique suffers from adrawback associated with a somewhat unpredictable sheet resistance thatis a function of the distance from the area of interest that the probetip is contacting to the position of the conducting via through thefront side of the chip.

A more difficult problem is associated with p-channel active areas in asemiconductor-on-insulator chip. In these circumstances, a conductingvia formed through the front side of the chip may yield information onlyon an extremely small portion of the chip that is within a particularsemiconductor device active island circumscribed by an isolationstructure. It may even prove difficult to fabricate diagnostic viawithout destructively altering the p-channel region.

The present invention is directed to overcoming or reducing the effectsof one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a method ofmanufacturing is provided that includes forming a bore from a backsideof a semiconductor chip through a buried insulating layer and to asemiconductor device layer of the semiconductor chip. A conductorstructure is formed in the bore to establish an electrically conductivepathway between the semiconductor device layer and the conductorstructure.

In accordance with another aspect of the present invention, a method ofmanufacturing is provided that includes forming a bore from a backsideof a semiconductor chip through a buried insulating layer and to asemiconductor device layer of the semiconductor chip. A conductorstructure is formed in the bore to establish an electrically conductivepathway between the semiconductor device layer and the conductorstructure. A diagnostic instrument is electrically connected to theconductor structure and the semiconductor device layer and a diagnostictest is performed on the semiconductor chip with the diagnosticinstrument.

In accordance with another aspect of the present invention, an apparatusis provided that includes a semiconductor chip that has a base substratewith a backside, a semiconductor device layer and a buried insulatinglayer positioned between the base substrate and the semiconductor devicelayer. A conductor structure is positioned in a bore extending from thebackside of the base substrate through the buried insulating layer andto the semiconductor device layer to establish an electricallyconductive pathway between the semiconductor device layer and theconductor structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings in which:

FIG. 1 is a sectional view of an exemplary conventional semiconductorchip substrate that has been retrofitted to enable scanning probemicroscopy for the purpose of performing a failure analysis on the chip;

FIG. 2 is another sectional view of the chip depicted in FIG. 1;

FIG. 3 is a sectional view of an exemplary embodiment of a semiconductorchip provided with a backside conductor structure;

FIG. 4 is a sectional view of the chip of FIG. 3 depicting exemplaryformation of a bore from the backside of the chip;

FIG. 5 is a magnified view of a portion of FIG. 4;

FIG. 6 is a sectional view of the chip of FIG. 3 depicting additionalexemplary processing of the bore;

FIG. 7 is a sectional view of the chip of FIG. 3 depicting additionalexemplary processing of the bore;

FIG. 8 is a sectional view of the chip of FIG. 3 depicting exemplaryformation of a conductor structure in the bore;

FIG. 9 is a sectional view of the chip of FIG. 3 depicting additionalexemplary formation of the conductor structure;

FIG. 10 is a sectional view of another portion of the chip of FIG. 3depicting an alternate exemplary formation of a bore from the backsideof the chip;

FIG. 11 is a sectional view like FIG. 10 but depicting alternateexemplary formation of a conductor structure in the bore; and

FIG. 12 is a sectional view of another portion of the chip of FIG. 3depicting another exemplary conductor structure.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In the drawings described below, reference numerals are generallyrepeated where identical elements appear in more than one figure.Turning now to the drawings, and in particular to FIG. 1, therein isshown a sectional view of an exemplary conventional semiconductor chipsubstrate 10 that has been retrofitted to enable scanning probemicroscopy (SPM) for the purpose of performing a failure analysis on thechip 10. The chip 10 is implemented as a silicon-on-insulator substratethat includes a bulk silicon base 15, a buried oxide layer 20 and a topsilicon active layer 25. The top active layer 25 is sub-divided intovarious device regions circumscribed by isolation structures 30 and 35.In this illustration, a device region 40 is circumscribed by theisolation structures 30 and 35. The isolation structures 30 and 35 mayactually be part of the same isolation structure. The device region 40includes a plurality of dopant regions 45, 50, 55 and 60. The dopantregions 45, 50, 55 and 60 are formed by establishing dopantconcentrations within the silicon active layer 25. A source/drain regionis a typical implementation of dopant regions such as the regions 45,50, 55 and 60. A scanning probe microscopy system 65 is used to performvarious types of scanning probe microscopy on the chip 10. The SPMsystem 65 includes a probe member 70 that has a probe tip 75 projectingdownwardly therefrom. The probe 70 is electrically connected to adiagnostic instrument 80. The diagnostic instrument 80 is operable toobtain signals indicative of properties of the chip 10 and the activelayer 25 thereof. The diagnostic instrument 80 typically includes anamplifier that may be a linear, logarithmic or other type. Thediagnostic instrument 80 is, in turn, connected to a voltage source 85.Another terminal of the voltage source 85 is connected to the back side90 of the bulk silicon base 15 by way of a conductor 95. In order forthe SPM system 65 to function properly, there must be an ohmic pathwaybetween the tip 75 and the conductor 95. This is not natively possiblewith the chip 10 due to the presence of the buried oxide layer 20. Toovercome this obstacle, a via 100 is formed in the chip 10 traversingthrough the active silicon layer 25, the buried oxide layer 20 and intothe bulk silicon base 15. The via 100 is conventionally established byetching a very deep trench 105 through the active silicon layer 25, theburied oxide layer 20 and into the bulk silicon base 15. Thereafter,platinum is deposited into the trench 105 to establish the via 100.

Assume for the purposes of this illustration that it is desired toperform an SPM analysis on an area of interest 110 in the active siliconlayer 25. In this illustration, the area of interest 110 is in thedopant region 50. With a tip 75 positioned proximate the area ofinterest 110 either in contact with the dopant region or slightly above,in the case of a capacitive test where a dielectric is in place, thevoltage source 85 is activated and a current pathway is establishedbetween the tip 75 and the conductor 95 such that a current i₁ can flowfrom the area of interest 110 through the dopant regions 50, 55 and aportion of 60 and down through the via 100 into the bulk silicon 15 andultimately to the conductor 95. The current is sensed by the amplifyinginstrument 80 and used to interpret the characteristics of the area ofinterest 110. Because the portion of the chip represented in FIG. 1, andin particular the device region 40, is a n-channel configuration, thecurrent i₁ can readily flow from the tip 75 across the expanse of thedevice region 40 and into the via 100. This is possible because thevarious dopant regions 45, 50, 55 and 60 are not individually isolatedby way of isolation structures such as the isolation structures 30 and35. Accordingly, data can be obtained using this conventional techniquefor re-channel regions. However, an issue does remain with regard to anartifact associated with the distance, x, from the tip 75 to the via100. There is a finite series resistance along the device region 40 fromthe tip 75 to the via 100. This series resistance is approximately equalto the device resistance at the area of interest 110. Therefor, themeasured electrical properties at the area of interest 110 will varydepending upon the distance x₁ from the via. This artifact can make theability of the system 65 to delineate fine electrical properties such asthe doping profile of a given dopant region 45, 50, 55 or 60 difficult.

Attention is now directed to FIG. 2, which is a sectional view ofanother portion of the semiconductor chip 10. At the portion of the chip10 depicted in FIG. 2, there are several p-channel device regions 115,120, 125 and 130 depicted. The device regions 115, 120, 125 and 130 areisolated laterally by way of isolation structures 135, 140, 145 and 150.The lateral isolation of particular device regions such as the regions115, 120, 125 and 130 is more typical for certain types of designs thatuse p-channel structures. Again, assume for the purposes of illustrationthat it is desired to perform a SPM analysis on an area of interest 155of the device region 115. In this regard, the device region 115 includesdopant regions 160 and 165 that are separated laterally to define achannel 170. There are similar dopant regions in the device regions 120and 125 that are not separately labeled. Again, the SPM system 65 ispositioned so that the tip 75 of the probe 70 is proximate the area ofinterest 155 and the conductor 95 is in ohmic contact with the back side90 of the bulk silicon base 15. Merely using another via 175 thatpenetrates through the device region 125 through the buried oxide layer20 and into the bulk silicon base 15 is not sufficient to establish anelectrical pathway between the probe 75 at the area of interest 155 andthe conductor 95 regardless of the sensitivity of the diagnosticinstrument 80. This follows from the presence of the interveningisolation structures 140 and 145 between the area of interest 155 andthe via 175. It might be possible to position individual vias inindividual device regions. However, this approach has the distinctpossibility of destroying the dopant regions in the device region andthus would not yield useful test results. Thus, for p-channel typeregions, the conventional apparatus and method shown in FIGS. 1 and 2 isinsufficient for performing SPM analysis.

An exemplary improved apparatus and method for performing SPM analysison an area of interest in a semiconductor chip may be understood byreferring now to FIG. 3, which is a sectional view of a small portion ofa semiconductor chip 180. The semiconductor chip 180 is implemented as asemiconductor-on-insulator design that includes a bulk semiconductorbase 185, an active semiconductor layer 190 and a buried insulatinglayer 195 sandwiched there between. The bulk semiconductor layer 185 maybe silicon, germanium, or another type of semiconductor as desired. Theactive semiconductor layer 190 may be composed of silicon, germanium, oranother type of semiconductor as desired. The buried insulating layer195 may consist of silicon dioxide, tetra ethyl ortho silicate, oranother type of insulating material as desired. The portion of thesemiconductor chip 180 visible in FIG. 3 includes a device region 200that is isolated laterally by way of respective isolation structures 205and 210. The device region 200 includes dopant regions 215, 220, 225 and230. The dopant regions 215, 220, 225 and 230 may be source/drainregions, resistors, or virtually any other type of region used in adevice region of a semiconductor chip. For purposes of thisillustration, assume that an area of interest 235 located in the dopantregion 220 is targeted for SPM analysis. By way of the SPM system 65that, as noted above, consists of a probe 70 with a downwardlyprojecting tip 75, the diagnostic instrument 80, a voltage source 85 anda conductor 95 that is designed to establish contact with thesemiconductor chip 180 so as to establish a current path between the tip75 and the conductor 95. Unlike the conventional design depicted inFIGS. 1 and 2 where via 100 or 175 is formed by etching a deep trenchdown through the active silicon layer, in this illustrative embodiment,a conductor structure 240 is formed in a bore 243 through the back side245 of the semiconductor base 185. The conductor structure 240 projectscompletely through the semiconductor base 185 and the buried insulatinglayer 195, and at least to, and in this illustrative embodiment intosomewhat, the active silicon layer 190. The conductor structure 240 isformed proximate the area of interest 235 targeted for SPM analysis. Inthis way, an ohmic pathway is established for a current i₂ to flowbetween the probe 75 and the conductor 95 which is electricallyconnected to the conductor structure 240.

In this illustrative embodiment, the conductor structure 240 consists ofa seed layer 255 that is then filled with a bulk conductor material 260.The seed layer 255 and the bulk conductor 260 may extend laterallyacross the surface of the back side 245 of the bulk semiconductor 185 asshown if desired. The conductor structure 240 may be fabricated atvirtually any location where an area of interest is positioned. In thisway, an ohmic pathway may be established between the probe 75 and theconductor 95 in very close proximity to area of interest 235 and thuswithout the unwanted artifact effects associated with the conventionaltechnique and the relationship to the distance between a conventionalvia and the area of interest. Furthermore, because the conductorstructure 240 can be positioned virtually anywhere proximate a deviceregion, p-channel devices may be readily subjected to SPM analysiswithout the constraints of the multiple isolation structures that wouldotherwise cutoff the current pathway as shown in FIG. 2.

An exemplary technique for fabricating the conductor structure 240depicted in FIG. 3 may be understood by referring now to FIGS. 4, 5, 6,7, 8, 9 and 10 and initially to FIG. 4. FIG. 4 is a sectional view ofthe semiconductor chip 180 flipped over with the bulk semiconductor base185 facing upward. Up to this point, the chip 180 has undergonedeprocessing by etching, polishing or other planarization techniques sothat any films and layers on the active semiconductor layer 190 thatwould obscure the device region 200 have been removed. The bore 243should be fabricated with two objectives: (1) avoid damaging thestructures in the active semiconductor layer 190; and (2) achieve a lowaspect ratio that will facilitate eventual material deposition. Toaccomplish these goals, the bore 243 may be formed in stages usingdifferent techniques. As shown in FIG. 4, the bore 243 is initiallyformed part way through the bulk semiconductor 185. Through subsequentprocess steps to be described below, the bore 243 will be extended tothe active semiconductor layer 190. Although a mask and etch schemecould be used to form the bore 243 at this stage, a less time consumingmaterial removal process may be appropriate, such as a laser assistedetch. In an exemplary embodiment, the bore 243 may be initially formedby laser assisted chlorine etching wherein a laser source 267 is used inconjunction with an atmosphere of chlorine. This particular chemistryand laser assist may be appropriate where, for example, thissemiconductor base layer 185 is composed of silicon. To ensure that thebore 243 will be accurately positioned, an infrared camera 270 may beused to locate the position of the area of interest 235 and a focusedion beam emitter 272 may be used to form fiducial marks 274 a and 274 bin the backside 245 of the semiconductor layer 185 around the area ofinterest. Any number of such fiducial marks 274 a and 274 b may beformed. With the fiducial marks 274 a and 274 b in place, the lasersource 267 may be accurately aimed and activated to conduct the etch. Itmay be necessary to stop the laser assisted etch short of the buriedinsulating layer 195 as shown in order to avoid overheating and possiblydamaging the circuit structures in the active semiconductor layer 190.If overheating is not a concern, then the etch could proceed to theburied insulating layer 195. The bore 243 may be rectangular, circular,oblong, oval, or other shapes. The lateral dimension x₂ of the top ofthe bore 243 may be determined by the laser spot size and/or themovement of the laser source 267 or the chip 180 in order to translatethe laser spot in different positions as desired. In an exemplaryembodiment, the laser radiation may be generated by an argon ion sourcewith dual wavelengths of 488 nm and 515 nm and have a spot size may beabout 1.0 micron. In order to facilitate subsequent material depositionsteps, the bore 243 is advantageously formed with a relatively lowaspect ratio. Accordingly, the side wall or walls 275 of the bore 243are advantageously inwardly sloping as shown.

As noted briefly above, the bore 243 is advantageously formed withsloped side walls 275 to lessen the aspect ratio of the bore 243. Inthis regard, attention is now turned to FIG. 5, which is a magnifiedview of the portion of FIG. 4 circumscribed by the dashed oval 280. Thebore 243 may be formed with a stair-stepped configuration as shown inFIG. 5. In this regard, the bore 243 may consist of a large diameterportion 282, a medium diameter or portion 285 and a smallest diameterportion 290. A stair-stepped construction such as that depicted in FIG.5 for the bore 243 may be necessary since a laser assisted chlorine etchis highly anisotropic and thus in order to provide an inwardly taperingprofile, several etches to provide the successively decreasing diameterportions 285 and 290 may be required. The number and sizes of theindividual stair-stepped portions 280, 285 and 290 that make up the bore243 are matters of design discretion.

Referring now to FIG. 6, the bore 243 is extended down to the buriedinsulating layer 195. While a variety of techniques may be used toaccomplish this material removal step, an exemplary embodiment utilizesa wet etchant that is active against silicon but relatively inactiveagainst silicon dioxide, such as tetra methyl ammonium hydroxide (TMAH).In order to prevent the wet etchant from attacking the various circuitstructures in the active semiconductor layer 190, an appropriate etchmask 300 may be applied to the semiconductor layer 190 prior to theetch. The composition of the etch mask 300 will depend upon the wetetchant selected. In an exemplary embodiment, a TMAH etchant is usedalong with a TMAH resistant material for the etch mask 300. Somedesirable properties for the mask material 300 include the readyadhesion to silicon and silicon dioxide, relative ease of removability,mechanical strength to protect the underlying circuit structures in thesemiconductor layer 190 as well as resistance to the TMAH etchant. In anexemplary embodiment, the etch resistant material for the mask 300 maybe a polymer, such as ProTEK. The mask 300 may be drop coated, spincoated or brushed on to a thickness of about 6.0 to 10.0 μm. A thermalcure at first at about 140° C. for about 2.0 minutes and subsequently atabout 205° C. for about 1.0 minute may be performed to finish the mask300.

In an exemplary etch recipe, the chip 180 may be placed in a bathconsisting of 60 ml of a 25% wt. water solution of TMAH mixed with 20 mlof isopropanol. The bath may be heated to about 83° C. Endpoint may beby timing determined from the etch rate and the thickness z ofsemiconductor remaining after the laser assisted etch. The etch rate ofsilicon using the just described TMAH bath is about 26 μm/hr. Thethickness z of semiconductor material remaining in the bore 243following the laser assisted etch may be determined with excellentaccuracy by, for example, the laser source 267, which includes anability to determine depth during focusing.

Referring now to FIG. 7, the bore 275 is extended down through theburied insulating layer 195. This material removal step may be performedby a variety of techniques. In an exemplary embodiment, a reactive ionetch is performed using the following recipe:

Base vacuum 2 × 10⁻⁵ Torr Pre-clean oxygen plasma for 3 min. 100 sccmoxygen pressure = 60 mTorr plasma forward power @ 60 W and 224 V DC EtchCHF₃ (25 sccm) + Ar (25 sccm) pressure = 30 mTorr plasma forward power @130 W Pump back 2 × 10⁻⁵ Torr Vent with N₂ atmosphere 760 TorrThis etch recipe yields an etch rate of about 18 nm/min. Endpoint mayagain be by timing. The thickness of the buried insulating layer 195will be known. For example, one exemplary insulating layer 195 may havea thickness of about 145 nm so the etch could be set to last about 8.0minutes. Again, it is desirable to maintain the inwardly slopingcharacter of the side walls 275 of the bore 243 in order to keep theaspect ratio of the bore 243 advantageously low. The etch 195 or othermaterial removal step used to penetrate the buried insulating layer 195advantageously extends the bore 243 at least to the semiconductor layer190 and may extend slightly into the layer 190 as depicted in FIG. 7. Anoptional in-situ ion milling step may be used to penetrate any nativeoxide on the exposed semiconductor layer 195. The mask 300 may beadvantageously left in place during etch of the bore 243 as desired.Depending upon the etch chemistry used for the reactive ion etch, someattack of the side walls 275 of the semiconductor base 185 may occur,albeit without adversely impacting the bore 243.

Attention is now turned to FIG. 8. After the bore 243 is fully formed,the seed layer 255 is formed in the bore 243 and may extend over theback side 245 of the bulk semiconductor layer 185 as shown if desired.The seed layer 255 is designed to readily adhere to the side walls 275of the bore 243 as not only in the silicon layer 185 but also the buriedinsulating layer 195. The seed layer 255 is also advantageously composedof a material that will readily adhere to the subsequently depositedconductor material 260 shown in FIG. 3. In a first exemplary embodiment,a graphite colloid suspension may be used for the seed layer 255. Anexemplary graphite colloid is 16053-SPC PELCO Colloidal Graphiteavailable from Pelco International in Redding, Calif. The graphitecolloid may be drop cast into the bore 243. In an exemplary embodiment,the graphite colloid is drop cast, allowed to settle at room temperaturein air and then thermally cured by slow ramp up to about 150° C. forabout 2.0 hours. The seed layer 255 should be applied either while thechip 180 is maintained in a vacuum or immediately after the completionof the bore 243 to avoid the formation of oxides in the bore 243proximate the semiconductor layer 1950 and the side walls of the bore243 in the semiconductor bulk base 185. In a second exemplaryembodiment, the seed layer 255 may consist of a metallic layer orlaminate. For example, a thin (approximately 35 nm) layer of sputteredtitanium may be followed with a thicker (approximately 350 nm) layer ofcopper, gold, palladium, mixtures of these or the like.

With the seed layer 255 in place, the chip 180 is ready to receive theconductor material 260. In this regard, attention is now turned to FIG.9, which shows the deposition of the conductor material 260 into thebore 243 and adhering to the seed layer 255. Portions of the conductor260 may extend out over the back side 245 of the semiconductor base 185as desired. A variety of materials may be used for the conductormaterial 260. In the first exemplary embodiment, a silver epoxy, such asEPO-TEK P1011 available from Epoxy Technology in Billerica, Mass., maybe drop cast and allowed to settle at room temperature and under vacuumconditions in the bore 243. The settling in vacuum allows any bubbles toescape from the silver epoxy. The silver epoxy may be subsequentlythermally cured by slow ramp up to about 150° C. for about 4.0 hours. Inthe second exemplary embodiment, copper may be plated to about a 30 to100 μm thickness to establish the conductor material 260.

Following the cure or plating of the conductor material 260, the etchmask 300 may be removed. A variety of techniques may be used to removethe etch mask. In one exemplary embodiment, a PROTEK material remover(MIAK) may be used to strip the mask 300 without damaging either theconductor 260 or the underlying circuit structures in the semiconductorlayer 190.

An alternate exemplary embodiment and process flow may be understood byreferring now to FIGS. 10 and 11. FIG. 10 is a sectional view of anotherportion of a semiconductor chip in which a bore 305 is formed extendingfirst through the bulk semiconductor base 185 by the techniquesdescribed elsewhere herein such as the laser assisted chlorine etch anda follow on XeF₂ gas etch in a flip chip focus ion beam chamber (notshown). These two processes are used to form the bore 305 down to theburied insulating layer 190. At this stage, an ion beam etcher 310 isused to direct an ion beam 315 into the bore 305 to drill down throughthe buried insulating layer 195 to the underlying semiconductor layer190. Again, both the laser assisted chlorine etch and the XeF₂ gas etchare advantageously performed so that an inwardly tapering side wall 325of the bore 305 may be provided. A stair-step arrangement like thatshown in FIG. 5 could be used.

Referring now to FIG. 11, following the ion beam etching of the buriedinsulting layer 195 down to and possibly into the semiconductor layer190, an in-situ ion beam deposition of a conductor material, such astungsten, may be performed to establish a conductor structure 330 in thebore 305. In this regard, tungsten-containing vapor 335 may beintroduced proximate the ion beam 315 in order to establish theconductor structure 330. Other materials suitable for the conductorstructure 330 include, for example, platinum, titanium,titanium-tungsten, gold or the like. If adhesion issue are contemplated,then laminates can be used, such as titanium followed by gold. As withthe other embodiment, an etch mask 300 may be used to protect theunderlying circuit structures of the semiconductor layer 190 during thematerial removal and deposition processes necessary to establish theconductor structure 330 in the bore 305.

FIG. 12 is a sectional view of another portion of the semiconductor chip180 that includes several p-channel active regions. In particular, threep-channel active regions 340, 345 and 350 are shown and isolatedlaterally by way of four isolation structures 355, 360, 365 and 370. Theisolation structures 355, 360, 365 and 370 and the active p-channelregions 340, 345 and 350 are all part of the active semiconductor layer190. Here, another backside conductor structure 375, which may becompositionally identical to any of the conductor structures disclosedelsewhere herein, is formed through the back side 245 of the bulksemiconductor layer 185 and established ohmic contact with not only theactive region 340, but also the active regions 345 and 350. Theconductor structure 375 is made large enough laterally to establishelectrical contact with multiple p-channel active regions 340, 345 and350. In this way, the limitations associated with the prior art and theblocking of lateral conductive pathways by isolation structures areovercome so that the SPM system 65 may be used to perform SPM analysison all of the active regions 340, 345 and 350 and compare them using acommon baseline. In this regard, the probe 75 tip may be positionedproximate the active region 340 and a current pathway i₃₄₀ isestablished from the probe tip 75 to the conductor 95 connected to thevoltage source 85. Similarly, current pathways i₃₄₅ and i₃₅₀ areestablished to and from the active regions 345 and 350 by way of theconductor structure 375. The diagnostic instrument 80 may function asdescribed elsewhere herein. Since the conductor structure 375 may belarge, overall sheet resistance will be lower and thus provide for moresensitive measurements of device characteristics. Furthermore, a largeconductor structure 375 can yield approximately equivalent sheetresistances for multiple areas of interest, which effectively cancelsout any artifact associated with distance from the conductor 375.

Any of the backside conductor structures disclosed herein may bepositioned wherever areas of interest of a semiconductor device arelocated. Once formed, the conductor structures enable a variety oftesting to be performed. Examples include conducting atomic forcemicroscopy, scanning spreading resistance microscopy, scanningcapacitance microscopy, scanning tunneling microscopy to name just afew. It should be understood that the structures and techniques could beapplied to other than CMOS devices.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. An apparatus, comprising: a semiconductor chip including a basesubstrate having a backside, a semiconductor device layer and a buriedinsulating layer positioned between the base substrate and thesemiconductor device layer; and a conductor structure positioned in abore extending from the backside of the base substrate through theburied insulating layer and to the semiconductor device layer toestablish an electrically conductive pathway between the semiconductordevice layer and the conductor structure.
 2. The apparatus of claim 1,wherein the conductor structure comprises a first conductive layer inthe bore and a second conductive layer on the first conductive layer. 3.The apparatus of claim 2, wherein the first conductive layer comprises agraphite colloid.
 4. The apparatus of claim 2, wherein the firstconductive layer comprises a metal.
 5. The apparatus of claim 1, whereinthe semiconductor device layer includes an area of interest, theconductor structure being positioned proximate the area of interest. 6.The apparatus of claim 1, comprising a diagnostic instrumentelectrically coupled to the semiconductor device layer and the conductorstructure.
 7. The apparatus of claim 6, wherein the diagnosticinstrument comprises a scanning probe microscope.